Electrical – How to wire up a 4-wire dimmer switch when I only have two 2 wires from the wall

dimmer-switchelectricalwiring

I'm replacing (yet again) my bathroom dimmer switch. The old switch had 3 wires: 2 black and one green. The two black wires were attached to the wires coming out of the wall and the green wire was attached to nothing. The new switch has 4 wires: black, red, red/white striped, and green. Can I attach the new switch somehow? If not, what would you recommend when I only have 2 wires (circa 1930) coming out of the wall (besides rewiring my house)?

Best Answer

Not sure what make and model dimmer you're trying to install, so I'll describe a common installation. Wire colors could vary, depending on manufacturer.

  • Black is the common terminal, and is attached to the ungrounded (hot) conductor feeding the switch.
  • Red is the switched lead (or a traveler in a 3-way installation), and is attached to the switched hot going to the light.
  • Red with white is a traveler, used for 3-way installations. In your situation, you'll just cap this one off.
  • Green is ground, and is attached to the grounding conductor.

Single pole installation
From Lutron Luméa® Installation Guide

If you don't have grounding conductors in your home, you could install a GFCI breaker and you'll be code compliant.

Lutron devices typically have a red and a red/white stripped wire, whereas Leviton has two red wires.